High-quality Ge-rich SiGe thin films epitaxially grown on Si at low temperature by a two-step approach

Abstract

In this paper, a two-step growth approach was proposed to deposit a Ge-rich Si_1−xGe_x epilayer directly on a Si substrate by reactive thermal CVD (RTCVD) at low temperature (350 °C). The two-step growth process included seed layer epitaxial growth, post-annealing, and a second epitaxial growth step. The effect of the two-step growth approach on the crystalline quality of the Si_1−xGe_x epilayer was investigated. Raman and TEM measurements indicate that a perfect Si_1−xGe_x film structure, with few in-film defects, can be achieved by the two-step approach, and the resulting Si_1−xGe_x films exhibited an RMS roughness of 1.02 nm with a threading dislocation density of ∼4.5 × 10⁵/cm² and a degree of strain relaxation of up to 100%. These results suggest that two-step growth, combined with annealing, is a good approach to fabricate a high-quality Si_1−xGe_x epilayer by RTCVD at low temperature.